This application claims the priority of Japanese application No. 29051, filed Jan. 28, 1998, the disclosure of which is expressly incorporated by reference herein.
1. Field of the Invention
The present invention relates to a small-sized device, provided with a LCD display and multiple switches (SWs), for measuring body fat percentage.
2. Description of the Prior Art
With the growing desire for health and good body form among people in recent years, the concerns about overweight control tends to shift from weight to body fat percentage. A weight measuring scale provided with a meter for measuring body fat percentage (hereafter referred to as a scale with fat meter) was proposed and is already on the market. A scale with a fat meter, however, is often larger than an ordinary scale, because electrodes and switches are necessary for measuring body fat percentage. A more small-sized scale having a fat meter is desired due to the house size conditions and other reasons. In a scale having a fat meter the space for installing an electronic circuit board is limited because a comparatively large space is occupied by associated mechanical parts such as electrodes, a scale mechanism, etc. for measuring body fat percentage. Further, the area of the circuit board is also limited by respective A/D portions which occupy a comparatively large area for measuring body fat percentage and weight.
A fat meter mainly employs an impedance method. In this method, a bio-impedance of a human body is measured and converted into an amount of fat. Accordingly, values of conversion parameters such as sex, height, age, weight, etc. of a measured person are necessary. Though weight can simultaneously be measured by a scale having a fat meter, other parameters must be input by the measured person. Since it is a nuisance to input these conversion parameters each time to measure body fat percentage, a scale provided with multiple "personal keys" is already on the market.
This scale is very handy because each "personal key" allows each measured person to register his or her own parameters such as sex, height, and age which are constant or do not change within a short period and each measurement can be implemented only by pushing each "personal key". This scale, however, usually demands 4 to 5 "personal keys" besides a key for setting these parameters.
Since a scale having a fat meter, compared with an ordinary scale, tends to display more information and to have more pins for LCD, providing more switches increases the number of control and input devices and the wires for these devices occupy a wider area. Conventionally, a LCD device was connected to a device for the LCD drive and a separate input device was used for a SW because of the problems described below.
The LCD display drive is generally so complicated that an exclusive device is required. Both the LCD display drive and the SW state detection must always be implemented. When a driver for a LCD and an input device for a SW are wired to an identical terminal, an abnormal indication occurs, for example, that a LCD segment not to be lit is lit because the electric potential of the terminal is set to either Hi or Lo depending on the SW state.
Though a control device (micro-controller) having both a LCD driver and an input device integrated is already on the market, the micro-controller must have many pins because both devices separately use respective pins. This naturally causes the micro-controller to be larger, demanding more space for wiring, and eventually makes it difficult to save space.
Though the use of a multi-layer interconnection board usually leads to a small-sized board, this manner allows only the wiring portion to be reduced and on the other hand greatly pushes up the cost of the board. Therefore, it has been difficult to reduce the board size.
The object of the present invention is to provide a means for a smaller and less expensive board for a body fat measuring device which has a LCD and multiple SWs and is constituted so as to allow a common terminal to be used simultaneously for both driving a LCD and inputting the SW state and so as to accomplish a smaller device with less terminals eventually.
According to an aspect of the present invention, there is provided a body fat measuring device comprising a body fat measuring sensor, a controller, a memory, a LCD driver, a LCD, and a SW for setting such personal data as sex, height, etc. for measuring the body fat percentage in a human body. At least one LCD drive terminal of said LCD driver, which works as a switchable terminal for either an input or an output, is connected to said SW directly or indirectly with a current limit element such as a resistor, therebetween. The terminal is usually set to work as an output terminal for driving said LCD. The terminal is periodically set to work as an input terminal for an input for a certain period negligibly shorter than a LCD drive period by the controller and thereby is set as a SW, and the input is stored into said memory.
According to another aspect of the present invention, there is provided a body fat measuring device for measuring the body fat percentage in a human body comprising a body fat measuring sensor, a controller, a memory, a LCD driver, a LCD, and a SW for setting such personal data as sex, height, etc. At least one LCD drive terminal of the LCD driver, which works as a switchable terminal for either an input or an output, is connected to the SW directly or indirectly with a current limit element such as a resistor therebetween. The terminal is usually set to work as an output terminal for driving said LCD. The terminal is periodically set to work as an input terminal for an input for a certain period negligibly shorter than a LCD drive period by the controller. During the certain period all common terminals are set to an intermediate voltage between the minimum and maximum of the driver voltage, and thereby is set as a SW, and said input is stored into said memory.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.